Characteristics of external noise of urban rail transit train

Based on the statistical energy analysis (SEA) theory and semi-infinite fluid method, a 6-group B-type train external noise simulation model was established. The vibration and wheel-rail noise excitations of the SEA model of the vehicle were determined via testing. An excitation was applied to the vehicle, and the external noise characteristics were calculated and analyzed. The model was verified through a passing-noise experiment on a rail transit train in a city in China. The contributions of each plate and the wheel-rail noise to the sound pressure level at the external point were discussed as well. Analysis results indicate that the SEA theory and semi-infinite fluid method can accurately predict the external noise of a train, with a computational efficiency 14.1 times that of the conventional approach. When the speed is 60 km•h-1, the significant frequency band at 7.5 and 30.0 m outside the vehicle is 400-1 600 Hz. The sound pressure level increases first and then decreases slowly with the increasing frequency. The variation trend is the same as that of the wheel-rail noise. The maximum amplitude frequency is 800 Hz, with the maximum values being 64.88 and 61.75 dB(A). The contributions to the external noise in decreasing order are those from the wheel-rail noise, window, side wall, door, floor, roof, and end wall. The noise radiated due to vehicle vibration contributes significantly to the low-frequency band. At the center frequencies of 20-100 Hz, the main sources of external noise are windows and side walls, the contribution rates are 21.2% and 19.2%, respectively. At the center frequencies of 100-500 Hz, the difference in the noise contribution rates of each plate and the wheel-rail system is insignificant. At the center frequencies of 500-5 000 Hz, the contribution rates of each plate of the train decrease gradually, and the contribution rate of the wheel-rail noise increases gradually with the increasing frequency, reaching more than 60% in the 1/3 octave band of 2 000-5 000 Hz. © 2021, Editorial Department of Journal of Traffic and Transportation Engineering. All right reserved.